Background and objective In-vivo MRI-guided drug delivery concept is a personalized technique towards cancer treatment. A major bottleneck of this method, is the weak magnetic response of nanoparticles. A crucial improvement is the usage of paramagnetic nanoparticles aggregates since they can easier manipulated in human arteries than isolated particles. However its significance, not a comprehensive study to estimate the mean length and time to aggregate exists. Methods The present detailed numerical study includes all major discrete and continues forces and moments of the nanoscale in a global model. The effort is given in summarizing the effects of particle diameter and concentration, and magnetic field magnitude to comprehensive relations. Therefore, several cases with nanoparticles having various diameters and concentrations are simulated as magnetic field increases. Results It is found that aggregations with maximum length equal to 2000nm can be formed. In addition, the increase of the concentration leads to a decrease in the amount of the isolated particles. Consequently, 33% of the particles are isolated for the concentration of 2.25mg/ml while 13% for the concentration of 10mg/ml. Moreover, the increase of the permanent magnetic field and diameter of particles gives rise to an asymptotic behavior in the number of isolated particles. Furthermore, the mean length of aggregates scales linear with diameter and magnetic field, however, concentration increase results in a weaker effect. The larger aggregation that is formed is composed by 21 particles. Smaller time is needed for the completion of the aggregation process with larger particles. Additionally, the increase of the magnitude of the magnetic field leads to a decrease in the aggregation time process. Therefore, 8.5ms are needed for the completion of the aggregation process for particles of 100nm at $B_0=0.1T$ while 7ms at $B_0=0.9T$. Surprisedly, the mean time to aggregate is of the same order as in microparticles, although, with an opposite trend. Conclusions In this study, the evolution of the mean length of aggregations as well as the completion time of the aggregation process in the nano and micro range is evaluated. The present results could be useful to improve the magnetic nanoparticles assisted drug delivery method in order to minimize the side effects from the convectional cancer treatments like radiation and chemotherapy.

背景和目的体内MRI指导的药物输送概念是针对癌症治疗的个性化技术。该方法的主要瓶颈是纳米颗粒的弱磁响应。关键的改进是顺磁性纳米粒子聚集体的使用，因为它们在人的动脉中比分离的粒子更易于操作。然而，它的重要性，而不是进行全面的研究以估计平均长度和聚集时间，并不重要。方法当前的详细数值研究在全局模型中包括了纳米尺度的所有主要离散力和连续力和矩。努力总结了粒径和浓度的影响，以及磁场强度对综合关系的影响。因此，随着磁场的增加，模拟了具有不同直径和浓度的纳米粒子的几种情况。结果发现可以形成最大长度等于2000nm的聚集体。另外，浓度的增加导致分离的颗粒的量减少。因此，分离出33％的颗粒，浓度为2.25 mg / ml，而13％的颗粒，浓度为10 mg/毫升。此外，永久磁场和颗粒直径的增加引起了分离颗粒数量的渐近行为。此外，聚集体的平均长度与直径和磁场成线性比例，但是，浓度增加导致效果较弱。形成的较大的聚集体由21个颗粒组成。完成较大颗粒的聚集过程所需的时间更短。另外，磁场强度的增加导致聚集时间过程的减少。因此，8.5毫秒需要用于聚合过程的完成为100的颗粒纳米处${乙}_0=0.1Ť$而在7毫秒时${乙}_0=0.9Ť$。令人惊讶的是，平均聚集时间与微粒中的平均时间相同，但是趋势相反。结论在本研究中，评估了纳米和微米范围内平均聚集长度的演变以及聚集过程的完成时间。本研究结果可用于改善磁性纳米粒子辅助药物的递送方法，以使对流性癌症治疗（如放射线和化学疗法）的副作用最小化。